Bottom Line: The research upon which the American Heart Association based their “eat-your-omega-6-fat” advisory, is fatally flawed, according to the results of a meta-analysis study, which showed that a steady diet of omega-6 polyunsaturated fatty acids increases the risk of heart disease and death, especially for women [1]. British J Nutr. Dec 2010.

[If you are having difficulty reading the entire post. Here's a link to the full post http://www.scribd.com/doc/44601571 ]

Background: Omega-6 fats are the most commonly eaten polyunsaturated fatty acids (PUFA) in westernized countries. The top three sources are corn oil, soybean oil and cottonseed oil, which are the main ingredients in margarines, salad dressings, and mayonnaise. Many studies have shown that PUFA lower cholesterol.

Prior to industrialization, no population has been exposed to the current high levels of omega-6 polyunsaturated fats. We evolved on a diet with a balanced proportion of omega-6 to omega-3 fats of about 1:1. Today, that ratio in westernized countries is out of whack, near 20:1 of omega-6 to omega-3 fats. Different farming practices, new food processing and the urging by health authorities to use vegetable oils in place of animal fats for heart health, triggered an onslaught of omega-6 fats into the food we eat.

While it’s true that PUFA lowers cholesterol, cholesterol is not they key culprit in heart disease. Inflammation is the “new cholesterol” in matters of eating to protect the heart (and other chronic diseases for that matter). Notably many inflammation medications work by blocking the effects of excess omega-6 fat, including statins, aspirin, and asthma inhalers.

In 1999, there was enough scientific evidence to prompt scientists to recommend an upper limit for omega-6 fats, to no more than 7 grams per day. This ceiling is based on eating a maximum of 3% fat calories from omega-6 fat on a 2000 calorie diet.

Yet, a decade later, the 2009 the American Heart Association (AHA) published a health advisory touting the benefits of eating a high omega-6 polyunsaturated fatty acids (PUFA), and warned that eating less than 5% of calories from omega-6 PUFA would be hazardous to heart health. [2-3].

The conclusion of AHA’s advisory were seriously questioned in part, because of their failure to:

-Distinguish the types of PUFA used in studies, which also substantially increased omega-3 fats, which are also PUFAs.

-Include relevant trials with unfavorable results and excluded poorly designed studies.

Notably, these studies did not provide the specific fat content of the experimental diets used to lower cholesterol. (Yet the AHA recommended to specifically increase omega-6 PUFA). These flaws prompted a team of National Institutes of Health (NIH) scientists to re-evaluate the data, using techniques resembling a scholarly forensic investigation.

Design: Nine randomized controlled trials (the gold standard of study design), were identified, which met the criteria of having an intervention diet high in PUFA and reported clinical outcomes.

Next came the detective work, worthy of an Agatha Cristy who-done-it. Most of the studies did not provide omega-3 fat data–it was just lumped together in the PUFA category.

In order to track down the missing fatty acid data, (many of these studies were conducted over 40 years ago), they had to dig through newspaper archives, public records, scientific proceedings from national conferences and correspond with the study investigators (or their colleagues, if deceased).

Once the fatty acid data was collected, they were segregated into two categories:

-Mixed Diet (containing both omega-6 and omega-3 polyunsaturated fatty acids.)

-Omega-6 Specific Diet

Then the data was pooled to evaluate the effect of the Omega-6 Specific Diet, compared to the effect of the Mixed Diet, on clinical outcomes. They also evaluated the potential confounding role of trans fatty acids.

Results: Here’s what they found when evaluating the composition of the intervention diets.

Diet Composition:

-Only three of the nine so-called PUFA studies were “pure” omega-6 intervention trials, which upped omega-6, without a concurrent rise in dietary omega-3. Combined, these three studies had 9,500 participants.
-Four of the studies increased both the omega-3 PUFA (EPA and DHA) and omega-6 PUFA, which totaled over 1,700 participants. Notably, the researchers discovered that the Oslo Diet-Heart Study provided about 5 grams of EPA and DHA per day to the intervention group. (That’s equivalent to about 16 fish oil capsules).
-The control diets had a mean estimated trans fatty acid content of 3% (a significant confounding factor, which unquestionably increases risk of heart disease).

Heart Disease and Death Outcomes

When the effects of the Omega-6 Specific Diet were compared to the Mixed Omega 6/omega-3 PUFA; the following health outcomes were discovered:

Omega-6 Specific Diet:
-Increased risk of heart disease and death, compared to the Mixed Diet intervention studies.
-The relative risk of cardiac death increased by 28%.
-Increased the risks of all relevant cardiovascular outcomes.
-There was only one study with women, which showed significant harm.

The Mixed Omega-6/Omega-3 Diet:
-There was 8% risk reduction of death from all causes.
-There was 22% risk reduction from heart disease death.

Conclusion: The scientists concluded, that not only is there no indication of health benefit, from increasing dietary omega-6 PUFA, but a possibility of harm. Therefore, they recommended that the public health advice to maintain or increase dietary omega-6 PUFA, should be reconsidered.

Study Quote: “The increased cardiovascular heart disease risks from omega-6 specific PUFA diets in our meta-analysis may be underestimated as omega-6 PUFA also replaced substantial quantities of trans fatty acids.”

An accompanying editorial applauded the “extensive detective work” by the NIH research team, led by Christopher Ramsden [4]

Commentary : There is more to this story. In my next post, I’ll describe what went on behind the scenes, as three NIH scientists from this study, tried to get letters to the editor published in the AHA’s scientific journal, Circulation, in response to their omega-6 advisory. (I was actually a participant and witness).

[1] Christopher E. Ramsden,Joseph R. Hibbeln,Sharon F. Majchrzak and John M. Davis (2010).Omega-6 Fatty acid-specific and mixed polyunsaturate dietary interventions have different effects on CHD risk: a meta-analysis of randomised controlled trials. British Journal Nutrition. Dec 2010; 104(11): pp 1586-1600. [2] Harris WS et al. Omega-6 Fatty Acids and Risk for Cardiovascular Disease. A Science Advisory From the American Heart Association Nutrition Subcommittee of the Council on Nutrition, Physical Activity, and Metabolism; Council on Cardiovascular Nursing; and Council on Epidemiology and Prevention. Circulation published January 26, 2009. [Free Full Text.] [3] American Heart Asssociation News Release. Omega-6 fatty acids: Make them a part of heart-healthy eating DALLAS, Jan. 27, 2009. [Free full Text] [4] Philip C. Calder (2010).The American Heart Association advisory on n-6 fatty acids: evidence based or biased evidence? British Journal Nutrition. Dec 2010; 104(11): pp 1575-1576.[Abstact]

Copyright © 2010 by Evelyn Tribole, MS, RD Published at www.EvelynTribole.com

•Rights to Reproduce: As long as you leave it unchanged, you don’t charge for it, and you include the entire copyright statement, you may reproduce this article.

DISCLAIMER: The information is intended to inform readers and is not intended to replace specific advice from a health care professional. Copyright 2010 Evelyn Tribole, MS, RD

For decades, Americans have been bombarded with conflicting arguments both for AND against this essential macronutrient. Should we eat them? Should we not? What kind of fat should we eat?

But the confusion stops here. My no-nonsense, easy to understand guide to all things fat will show you why breaking-up with your beloved fat is not the way to go.

Why do we need fat?
-Critical for the production of cells and hormones in our bodies
-Important for proper brain functioning
-Provides energy
-Regulates the nervous system
-Controls blood pressure, heart rate and blood clotting
-Essential for the absorption of vitamins (particularly A, D, E, K)

How much do we need?
The daily recommended consumption of total fat in our diet should fall between 20-35%, with 10% or less saturated fats and 1% or less trans fats.

So, if you eat 2,000 calories a day, and 30% of that is fat, you are consuming 600 calories of total fat in your diet.

A common misperception about fats is that the good-for-you fats are also lower in calories. While some fats are healthier than others, they all share the same caloric density (~9 calories per gram). But don’t let that scare you.

Who are the key players? (from worst to best)

Trans Fat
Why it’s the worst:
-Raises LDL (bad guy) cholesterol
-Lowers HDL (good guy) cholesterol
Found in: Stick Margarine; Baked goods; Fried foods; Any foods with “hydrogenated” or “partially hydrogenated” in the ingredient list

Saturated Fat
Why it’s bad:
-Raises LDL (bad guy) cholesterol
Found in: Animal fats (meat, whole milk, ice cream, cheese, butter); Certain plant oils (coconut oil, palm oil, cocoa butter)

Polyunsaturated Fat
Why it’s good:
-Lowers total cholesterol
Found in: Vegetable oils (safflower, corn, sunflower, soy oils)

Omega 3 Fatty Acids (type of polyunsaturated fatty acid)
Why it’s better:
-Lowers total cholesterol
-Lowers triglycerides
-Decreases blood clotting
-Decreases inflammation
Found in: Fatty fish (salmon, mackerel, herring), Walnuts, Flaxseeds (and flaxseed oil)

Monounsaturated Fat (MUFA)
Why it’s the best:
-Protects against heart disease (lowers LDL cholesterol, raises HDL cholesterol)
-Prevents obesity related diseases such as diabetes and metabolic syndrome
-Maintains brain function
-Decreases inflammation
-Reduces risk of prostate cancer
-Targets stubborn belly fat
Found in: Oils (Canola, safflower, sesame, soybean, walnut, flaxseed, sunflower, olive and peanut oils); Olives; Nuts and Seeds; Avocados; Dark chocolate

Here’s a simple mantra to follow:

Instead of LOW/NO fat, think GOOD fat…and in moderation.

For an even more in-depth look at how fats can affect your health, check out my New York Times bestselling book, Flat Belly Diet! For Men.

View a synopsis here: http://www.sciencedaily.com/releases/2009/09/090914110533.htm.